Many therapeutic proteins and other drugs have been found to have a short half-life in circulation and short-lived bioavailability. The half-life is dictated by specific and non-specific clearance mechanisms and the rate of degradation of the protein or drug. As a consequence of this short-lived bioavailability, high initial doses and frequent dosing regimens may be required to sustain therapeutic levels of drug, potentially resulting in dose-related toxicities, poor patient compliance and increased treatment cost. Methods are required that will increase protein and drug half-life while sustaining protein activity. An ideal method for this purpose would increase protein half-life by attachment to a readily available biocompatible polymer using a simple and scaleable process.
Attachment (e.g., conjugation) of drugs and proteins to macromolecular carriers is a known means of increasing drug and protein half-life. The current known conjugation methods concentrate on reactions that form an irreversible attachment between the macromolecular carrier and the drug or protein. One example of such bioconjugation is the attachment of proteins to the non-natural carrier, polyethylene glycol (PEG), a process termed PEGylation. PEGs are synthetic polymer strands that can be chemically activated for attachment to proteins, usually through a single point of attachment of the PEG molecule to the protein, to increase the size of the protein. A variety of PEGylated protein conjugates have been disclosed, for example, in U.S. Pat. No. 4,002,531, U.S. Pat. No. 5,122,614 and U.S. Pat. No. 5,824,784. Conjugates such as PEG-interferon have been approved for use in the treatment of hepatitis C virus infection and demonstrate a longer half-life and lower dosing frequency compare to unmodified interferon (IFN). Other PEGylated proteins, including PEGylated versions of G-CSF, blood clotting factors, enzymes and other high value therapeutic proteins, are currently in clinical use or under development. One key drawback is that often PEGylated proteins only sustain a fraction of the activity of the native protein since the PEG is attached directly to, or is located near to, sites on the protein that are required for activity. For example, PEGylated interferon-α2a (Roche's Pegasys® and PEGylated interferon-α2b (Schering's Pegintron®), which are approved drugs, have only 6% and 28% of the activity of their corresponding unmodified interferons, respectively, and PEGylated asparaginase (Enzon's Oncaspar®), an approved anti-cancer treatment, has only 50% of the activity of unmodified asparaginase. Furthermore, PEGylation methods result in irreversible attachment of the PEG to the protein, such that the protein is permanently modified in its lower activity PEG-protein form, and is not released in a more active form. As such, PEGylation requires careful selection of the protein drug modification site to minimize loss of activity.
Other ways to increase drug half-life include the production of fusion proteins (e.g., albumin-IFN) or the addition of new glycosylation sites to proteins (e.g., glycosylated erythropoietin) through genetic manipulation, as well as, chemical modification to cross-link, stabilize and polymerize proteins (e.g., o-raffinose- or glutaraldehyde-polymerized hemoglobin). Each of these approaches requires careful selection of the site of modification to minimize loss of protein activity.
Polysaccharide modification of proteins has also been used to increase the half-life of proteins. Polysaccharides are naturally occurring macromolecules that may be more biocompatible than synthetic polymers used for protein conjugation. In a typical polysaccharide conjugation process, vicinal diols of the polysaccharide are oxidized to form aldehydes that can react with amines on the protein by a reductive amination process to form stable secondary amine linkages. The oxidised polysaccharide initially reacts with the protein to produce an imine intermediate that is reduced under the reaction conditions to a stable secondary amine linkage. Typical reducing agents used to carry out the reductive amination process include sodium cyanoborohydride, sodium borohydride and dimethylamino borane, among others. For example, U.S. Pat. No. 4,356,170 discloses covalently linking a protein to an oxidised antigenic polysaccharide via an amine linkage formed by reductive amination to form a stable conjugate. The formation of a stable conjugate that does not dissociate under physiological conditions is important because the authors report an oxidised polysaccharide-tetanus toxoid conjugate that showed enhanced immunological properties compared to the initial polysaccharide antigen. US 2005/0063943 discloses a conjugate of hydroxyalkyl starch covalently bonded to an active agent (such as a protein) via an amine linkage formed by reductive amination. US 2005/0063943 also discloses using a linker to indirectly connect the hydroxyalkyl starch to an active agent via reductive amination. US 2007/0134197 discloses conjugates of hydroxyalkyl starch and a protein formed by reductive amination. Conjugation was through single point attachment between the hydroxyalkyl starch and the protein. Under the disclosed reductive amination conditions the hydroxyalkyl starch and the protein inevitably produce a secondary amine product. The importance of using reducing conditions was demonstrated by a control reaction between an aldehydo-hydroxyethyl starch and erythropoietin (EPO), which failed to produce any conjugate in the absence of reducing agents. U.S. Pat. No. 5,177,059 discloses conjugating polymyxin B to dextran via either a carbamate linkage or an amine linkage via reductive amination. In each of these cases, reductive amination is used to form conjugates of proteins with oxidised polysaccharide. However, such amine linkages are not reversible (i.e., the bond between the oxidised polysaccharide and the protein is not dissociated by processes such as non-enzymatic hydrolysis or transimination under physiologic conditions).
Proteins have also been conjugated to oxidized polysaccharides without reduction to form imine-linked conjugates. U.S. Pat. No. 5,554,730 discloses a method of preparing a stable immunogenic polysaccharide-protein conjugate microparticle. This method oxidises a polysaccharide and then combines it with a protein to form a Schiff base conjugate. This method requires the presence of a macromolecular crowding agent in order to form the conjugate microparticle. The polysaccharide is chosen from bacterial antigens capable of inducing an immune response when coupled to a protein. Hence, in order to produce the desired immune response, it is important to select components that form a conjugate that does not readily dissociate under physiologic conditions. Indeed, in the sole example an immunogenic capsular polysaccharide derived from bacteria is conjugated to a protein, tetanus toxoid that is also immunogenic. U.S. Pat. No. 6,011,008 discloses conjugates prepared by oxidising polysaccharides such as dextran or arabinogalactan to a dialdehyde and reacting with a low molecular weight drug or polypeptide to form a Schiff base conjugate. This method aims to provide a stable water soluble conjugate whose biological activity is comparable to the activity of the free substance. Hence, components were chosen that do not readily dissociate once a conjugate is formed. The degree of oxidation in the dialdehyde varied from 5 to 50%. Dextran and arabinogalactan contain large numbers of 1,2,3-triol monomer units that upon oxidation form alpha-hydroxy aldehydes that can form irreversible linkages to polypeptides in the absence of reduction. Such irreversible linkages are formed by an Amadori rearrangement. These irreversible linkages limit the release or dissociation of the protein from the conjugate. Protein release was less than 30% in all examples of non-reduced conjugates in U.S. Pat. No. 6,011,008. U.S. Pat. No. 6,956,119 discloses conjugates prepared by partially oxidising polysaccharides such as dextran or mannan and reacting them with an antigenic polypeptide. In particular, U.S. Pat. No. 6,956,119 teaches selecting mannan as the polysaccharide so that the corresponding conjugate is taken up by cells that carry the mannose receptor. Both dextran and mannan contain 1,2,3-triol monomer units that upon oxidation form alpha-hydroxy aldehydes that can form irreversible linkages to polypeptides.
All of the current methods to modify proteins to increase half-life have limitations that may be addressed by alternative protein modification strategies. The ideal composition of a polymer-protein conjugate for increased protein half-life and sustained activity is one in which the majority of the polymer-protein linkages are reversible. Such linkages between the polymer and the protein are dissociated by processes such as non-enzymatic hydrolysis, cleavage or transimination under physiological conditions. Such conjugates avoid the problems of decreased activity observed with many known conjugates. Thus, there is a need for conjugates that reversibly attach a protein to a carrier enabling increased protein half-life and allow for release of the protein in an active form to provide sustained activity.
The inventors have discovered an efficient and widely applicable method to prepare compositions of reversible polysaccharide-protein conjugates and increase protein half-life and sustain activity. The method does not require modification site selection as necessary for many of the previously reported methods. Compositions are prepared using polysaccharides, such as those with low 1,2,3-triol contents, that do not form significant amounts of alpha-hydroxy aldehydes upon oxidation in order to minimize the formation of irreversible linkages in the absence of reduction. Proteins are readily reacted with the oxidized polysaccharide to produce conjugates with optimal product size and protein load, improved stability and sustained bioactivity. Through appropriate selection of polysaccharide-protein reaction conditions, the stability of the conjugate can be adjusted to provide the desired protein release profile.
In one aspect the present invention provides a method of preparing a composition comprising an oxidised polysaccharide-protein comprising the steps of:                (a) oxidising a polysaccharide with an oxidising agent to form an oxidised polysaccharide; and        (b) reacting the oxidised polysaccharide with a protein to form a composition comprising an oxidised polysaccharide-protein conjugate wherein the oxidised polysaccharide and the protein are conjugated via one or more imine bonds; and wherein the oxidised polysaccharide comprises essentially no alpha-hydroxy aldehyde units.        
In another aspect, the present invention provides an oxidised polysaccharide-protein composition comprising an oxidised polysaccharide and a protein; wherein the oxidised polysaccharide comprises essentially no alpha-hydroxy aldehyde units and wherein the protein is conjugated to the oxidised polysaccharide via one or more imine bonds.
In another aspect the present invention provides an oxidised polysaccharide-protein composition obtained by a method as described herein.
In another aspect the present invention provides an oxidised polysaccharide-protein composition for use in the treatment or diagnosis of a disease or condition wherein the composition comprises an oxidised polysaccharide and a protein; wherein the oxidised polysaccharide comprises essentially no alpha-hydroxy aldehyde units and wherein the protein is conjugated to the oxidised polysaccharide via one or more imine bonds; and wherein the disease or condition is selected from hormone deficiency, hemostasis, thrombosis, metabolic enzyme deficiency, pulmonary disorder, gastrointestinal disorder, immunodeficiency, hematopoiesis, fertility disorders, immunoregulation, endocrine disorders, hemophilia, shock, growth regulation, cancer, transplantation, infectious disease, inflammation and detoxification.
In another aspect, the present invention provides an oxidised polysaccharide-protein composition wherein the protein is conjugated to the oxidised polysaccharide via one or more imine bonds.
The polysaccharide-protein compositions, their preparation processes and uses as described herein offer several advantages over those of previously disclosed protein conjugates. Previous conjugates prepared by linkage of a protein to polymers such as PEG and polysaccharide have decreased protein activity as a result of irreversible modification of sites on the protein essential for activity. Such conjugates had reduced protein activity upon analysis or following administration. Attempts to limit this decrease in activity require site-specific chemistry methods and careful selection of specific polymer attachment sites on the protein. Therefore, in the field of therapeutic protein conjugate compositions intended to increase half-life and duration of activity in vivo, there is a need for conjugates of polysaccharide and protein with the ability to regain activity or to increase activity following administration, by minimizing the number of irreversible linkages between the polysaccharide and the protein.
The compositions described herein comprise a soluble mixture of a protein and a polysaccharide, wherein the composition allows for the sustained release of protein in the circulation with all the added benefits of such a sustained release technology. The composition preferably comprises a combination of a protein and a polysaccharide wherein the composition is capable of releasing the protein in an active form. Protein activity may be initially decreased as a result of linkage to the polysaccharide, and lost activity may be partially or totally regained upon release from the linked polysaccharide-protein conjugate form. In this way, the total protein specific activity may increase following administration. The linked polysaccharide-protein conjugate is comprised of oxidized polysaccharide molecules covalently linked to protein molecules via linkages that permit release of the protein from the polysaccharide component. The linkages are imine bonds (also known as or Schiff bases or azomethines), which can be released or dissociated by non-enzymatic hydrolysis or transimination via peptides, amino acids, proteins or other endogenous amines in plasma. The linkages are formed between aldehyde groups on the oxidized polysaccharide and amino groups on the protein by condensing under selected conditions. These linkages preferably account for all or the majority of linkages in the composition.
Compositions comprising the conjugate are preferably adjusted to a pH, ionic strength and concentration to maintain the majority of the total protein in the linked polysaccharide-protein conjugate form prior to administration to an animal or use under conditions requiring the release of the protein from the composition.
Properties of the conjugate were found to be controlled though selection of reaction parameters including the degree of polysaccharide oxidation, the size and polydispersity of the polysaccharide, the degree of hydroxyethylation, the ratio of oxidized polysaccharide to protein, the concentration of the protein, as well as reaction pH, temperature and time. These reaction conditions have been found to affect properties of the conjugate or of compositions comprising the conjugate. Selection of reaction parameters is used to control properties of the composition including the amount of protein conjugated to the polysaccharide, the rate of release of protein, the activity of the modified protein in the composition, the time-activity profile of the protein in solutions containing the composition, circulatory half-life of the protein and its in vivo biodistribution and activity, as well as the stability, solubility, and immunogenicity of the protein.
Composition
Preferably the oxidised polysaccharide-protein composition is obtained by a method as described herein.
In some aspects, the composition may further comprise a non-conjugated protein.
In another aspect, the present invention provides a composition comprising:
(i) an oxidised polysaccharide-protein conjugate as described herein; and
(ii) non-conjugated protein;
wherein the non-conjugated protein (ii) provides initial activity and the conjugated protein (i) provides sustained activity.
In another aspect, the present invention provides a method of providing enhanced activity of a protein in a patient comprising the step of administering to a subject a composition as described herein.
In another aspect, the present invention provides a method of providing enhanced activity of a protein in a patient comprising the step of administering to a subject a composition comprising:
(i) an oxidised polysaccharide-protein conjugate as described herein; and
(ii) non-conjugated protein
wherein the non-conjugated protein (ii) provides initial activity and the conjugated protein (i) provides sustained activity.
In another aspect, the present invention provides a composition comprising:
(i) an oxidised polysaccharide-protein conjugate as described herein; and
(ii) non-conjugated protein;
for the treatment of a disease,
wherein following administration of the composition the non-conjugated protein (ii) provides initial activity and the conjugated protein (i) provides sustained activity.
Preferably, the conjugated protein (i) enhances the circulatory half-life (t1/2) relative to the circulatory half-life of non-conjugated protein.
Thus, depending on the level of purification applied or duration of reaction, the composition can contain a fraction of the total protein content in non-conjugated (i.e. in non-bound or free) form, either by addition of the protein, or in the form of unreacted protein residual from the reaction of the oxidised polysaccharide with the protein or in the form of non-conjugated (or free) protein in equilibrium with reversibly bound form in the conjugate. A fraction of free protein in the composition may provide immediate activity upon administration of the composition, and may also exist in equilibrium with the reversibly bound form of protein to maintain a fraction of the total protein in bound form.
The composition may also comprise an excipient suitable for administration to a human or an animal. Such excipients could include amino acids or other proteins.
Suitably the ratio and concentration of non-conjugated protein to polysaccharide-conjugated protein in the composition are controlled to maintain a substantial proportion of the protein in the conjugated form. Preferably the proportion of the protein in the conjugated form is greater than or equal to 50%; preferably, greater than or equal to 60%; preferably greater than or equal to 70%; preferably greater than or equal to 80%; preferably greater than or equal to 90%.
The concentration of total protein in the composition may be adjusted to maintain an equilibrium ratio of non-conjugated protein to polysaccharide-bound protein of less than 0.5:1; preferably less than 0.4:1; preferably less than 0.3:1; preferably less than 0.2:1; preferably less than 0.1:1.
Preferably, the composition is a liquid formulation.
Preferably, the composition is soluble; preferably soluble in aqueous solvent; preferably soluble at physiological pH; preferably soluble in the absence of glycol, polyvinylpyrrolidone and/or macromolecular crowding agents.
Preferably, the oxidised polysaccharide-protein composition further comprises at least one further protein and each protein is conjugated to the oxidised polysaccharide via one or more imine bonds. Preferably there is one further protein. Suitably, the protein is streptokinase and the further protein is albumin.
Conjugate
In a further aspect, there is provided a method of preparing an oxidised polysaccharide-protein conjugate comprising the steps of:                (a) oxidising a polysaccharide with an oxidising agent to form an oxidised polysaccharide; and        (b) reacting the oxidised polysaccharide with a protein to form a conjugate wherein the oxidised polysaccharide and the protein are conjugated via one or more imine bonds; and wherein the oxidised polysaccharide comprises essentially no alpha-hydroxy aldehyde units; and optionally        (c) lowering the pH of the oxidised polysaccharide-protein conjugate to a pH of from 5 to 6 for formulation purposes.        
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate prepared by a method as described herein.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate as described herein for the treatment or diagnosis of a disease or condition wherein the conjugate comprises a protein conjugated to the oxidised polysaccharide via one or more imine bonds.
Preferably the oxidised polysaccharide-protein conjugate is soluble; preferably soluble in aqueous solvent; preferably soluble at physiological pH; preferably soluble in the absence of glycol, polyvinylpyrrolidone and/or macromolecular crowding agents.
Preferably the oxidised polysaccharide-protein conjugate is less than 0.1 μm in size; preferably less than 0.09 μm; preferably less than 0.08 μm; preferably less than 0.07 μm.
Preferably the oxidised polysaccharide and the protein are conjugated via two or more imine bonds.
Half-Life
In another aspect, the present invention provides an oxidised polysaccharide-protein composition or conjugate as described herein wherein the circulatory half-life (t1/2) of a protein that is conjugated is enhanced relative to the circulatory half-life of a non-conjugated protein.
In another aspect, the present invention provides an oxidised polysaccharide-protein composition or conjugate as described herein wherein the circulatory half-life (t1/2) or bioactivity of a protein that is conjugated is enhanced relative to the circulatory half-life or activity of a non-conjugated protein by gradually releasing the protein from the conjugate over time.
Suitably the composition allows gradual release of an active protein in circulation. Suitably the composition allows gradual release of an active protein in circulation at physiological pH. Suitably the gradual release occurs by processes such as non-enzymatic hydrolysis or transimination under physiological conditions. Suitably oxidised polysaccharides with varying degrees of oxidation as described herein are conjugated to the protein to allow gradual release of the protein in circulation. Suitably oxidised polysaccharides with varying weight average molecular weights as described herein are conjugated to the protein to allow gradual release of the protein in circulation.
Uses
In a further aspect, there is provided a use of a polysaccharide as described herein in the manufacture of a medicament comprising an oxidised polysaccharide-protein composition, wherein the oxidised polysaccharide is present in the composition in an amount sufficient to prolong the bioavailability and/or bioactivity of the protein in the circulation of a subject.
In a further aspect, there is provided a use of an oxidised polysaccharide-protein composition as described herein in the manufacture of a medicament wherein the circulatory half-life (t1/2) or bioactivity of a protein that is conjugated is enhanced relative to the circulatory half-life of a non-conjugated protein.
In a further aspect there is provided a use of an oxidised polysaccharide-protein composition as described herein in the manufacture of a medicament wherein the composition comprises a conjugate such that the circulatory half-life (t1/2) or bioactivity of a protein that is conjugated is enhanced relative to the circulatory half-life of a non-conjugated protein.
In a further aspect, there is provided a use of a composition comprising:
(i) an oxidised polysaccharide-protein conjugate as described herein; and
(ii) non-conjugated protein;
in the manufacture of a medicament for the treatment of a disease,
wherein following administration of the composition the non-conjugated protein (ii) provides initial activity and the conjugated protein (i) provides sustained activity.
The conjugates, compositions and processes can be used as follows (either independently or in combinations):                as a therapeutic or diagnostic agent for human use.        to increase the half-life of the protein.        to increase the activity of the protein in vitro.        to preserve the activity of the protein in vitro.        to increase the activity of the protein in vivo.        to preserve the activity of the protein in vivo.        to sustain the activity of the protein.        to sustain the activity of the protein wherein the sustained activity is a result of the release of protein in plasma.        to delay the activity of the protein.        to administer the protein with reduced activity compared to non-conjugated protein, wherein the protein activity is recovered or increased following administration.        to administer an enzyme with reduced total specific activity compared to non-conjugated enzyme, wherein the total specific activity increases following administration.        to provide a latent form of an enzyme, which becomes more active during circulation in the body.        to provide a form of protein that has reduced ability to interact with endogenous activating or inhibiting agents, wherein this ability is recovered following administration.        to provide a form of protein that has reduced ability to interact with endogenous substrates or receptors or ligands, wherein this ability is recovered following administration.        to stabilize the protein.        to temporarily decrease activity of the protein.        to increase solubility of the protein.        
In one aspect, there is provided the use of an oxidised polysaccharide-protein composition described herein to solubilise insulin.
Polysaccharide
Preferably the polysaccharide is a polysaccharide that contains essentially no 1,2,3-triol monomer units (defined as R—CHOH—CHOH—CHOH—R′). 1,2,3-triol monomer units are also known as alpha-beta-gamma-triol monomer units.
The proviso that the polysaccharide contains essentially no 1,2,3-triol monomer units means that preferably less than about 20% of the total polysaccharide monomer units are 1,2,3-triol monomer units. Preferably less than about 15% of the total polysaccharide monomer units are 1,2,3-triol monomer units; preferably less than about 10%; preferably less than about 5%; preferably less than about 3%; preferably less than about 2%; preferably less than about 1% are 1,2,3-triol monomer units.
The amount of 1,2,3-triol monomer units may be calculated from a consideration of the particular polysaccharide being used. For example, hydroxyethyl starch (HES) is made from natural corn starch amylopectin and consists of D-glucose monomers linked via linear α1,4 linkages. Typically in HES, approximately half of the glucose monomers are hydroxyethylated at one or more of their hydroxyl groups through an industrial hydroxyethylation process, to minimize degradation of the HES by amylase in vivo. Higher or lower hydroxyethylation ratios may also be used to prepare HES. The α1,4 linked glucose monomers (linked to neighboring glucose monomers at both the C1 and C4 hydroxyl groups, and also at C6 if at a branch point) contain vicinal diol groups (at C2 and C3), but no 1,2,3-triol groups. The branch end points do contain 1,2,3-triol groups (at C2, C3 and C4) and can form alpha-hydroxy aldehyde groups upon oxidation, which would undergo the Amadori rearrangement if they react with protein. Likewise, the first monomer in the polymer also contains a 1,2,3-triol group (at C1, C2 and C3).
Relevant information for calculating the amount of 1,2,3-triol monomer units such as the branching frequency may be estimated from structural studies using a combination of periodate oxidation and hydrolysis followed by analysis of formic acid, formaldehyde, and other fragments (for example, see “Periodate Oxidation of Diol and Other Functional Groups” by Glenn Dryhurst, Vol. 2 in the series “Monographs in Organic Functional Group Analysis”, Pergamon Press, 1970).
The branching frequency in HES is 1 in every 17-20 monomers. Hence, ˜5-6% of all glucose monomers in HES would be end points. Not all of these would contain 1,2,3-trial groups, however, because of the hydroxyethylation in HES. Since only ˜5-6% of glucose monomers are end groups, and half of these are hydroxyethylated, and because modification of the C2 hydroxyl group accounts for at least two-thirds of hydroxylethylation in HES, then ˜3% of HES monomers will contain 1,2,3-triol groups.
Preferably, the polysaccharide is selected from cellulose, pectin, starch and hydroxyhydrocarbyl derivatives thereof.
Preferably the polysaccharide is selected from cellulose, pectin, starch and hydroxyalkyl derivatives thereof. In polysaccharides containing 1,2,3-triol groups, hydroxyalkylation of one or more of the hydroxyl groups in the triol will prevent oxidation of the triol, and prevent the formation of alpha-hydroxy aldehyde groups upon oxidation.
Preferably, the polysaccharide is selected from starch and hydroxyhydrocarbyl derivatives thereof; more preferably the polysaccharide is selected from starch and hydroxyalkyl starch.
Preferably, the polysaccharide is hydroxyethyl starch.
The polysaccharide can be selected from polysaccharides containing vicinal diol groups capable of being oxidized to form dialdehydes, and excluding polysaccharides such as dextran and other similar polysaccharides that, following oxidation, can potentially form irreversible linkages with proteins via the Amadori Rearrangement.
A wide range of natural and modified polysaccharides, varying in size and chemical properties, are available.
The polysaccharide to be used in the present invention may optionally be modified prior to oxidation to alter its stability and biodistribution properties, for example by hydroxyethylation, and by selection of the degree and location of these modifications.
A wide range of proteins may benefit from the various modifications of the polysaccharide, including those requiring release of unmodified protein for optimal activity, proteins benefiting from polymerization to increase activity or for multiple presentations of the protein on the conjugate surface, or to increase half-life and lower clearance. Through appropriate design, the polysaccharide modification may be ideally suited for increasing enzyme half-life while maintaining activity, or masking activity until release.
Preferably the oxidized polysaccharides are polyfunctional, meaning that more than one sugar monomer is oxidized. Where more than one sugar monomer is oxidized, more than two aldehyde groups are formed in the polysaccharide. Polyfunctionality permits polymerization through the polysaccharide, or permits multiple points of attachment between the oxidized polysaccharide and the protein. The degree of polyfunctionality of the oxidized polysaccharide is controlled by the degree of oxidation of the polysaccharide; higher levels of oxidation produce higher levels of polyfunctionality. A higher polyfunctionality can provide for more attachment sites between the oxidized polysaccharide and the protein, and thereby influence the degree of modification and rate of release of the protein from the oxidized polysaccharide, with a greater number of attachment points providing a slower rate of release of the protein.
Preferably, the polysaccharide is a branched polysaccharide. Preferably the degree of branching occurs at less than 1 in 30 monomer units; preferably less than 1 in 25 monomer units; preferably less than 1 in 20 monomer units; preferably less than 1 in 15 monomer units; preferably less than 1 in 10 monomer units; preferably less than 1 in 5 monomer units.
Hydroxyhydrocarbyl Derivatives
Hydroxyhydrocarbyl derivatives of polysaccharides are derivatives where a —OH group of the polysaccharide has been replaced with a —O—R1—OH group, wherein —R1— is a hydrocarbyl group.
The term “hydrocarbyl group” as used herein means a group comprising at least C and H. Also, the hydrocarbyl group may optionally comprise one or more other suitable substituents. Examples of such substituents may include halo-, alkoxy-, nitro-, a hydrocarbon group, an N-acyl group, a cyclic group etc. In addition to the possibility of the substituents being a cyclic group, a combination of substituents may form a cyclic group. If the hydrocarbyl group comprises more than one C then those carbons need not necessarily be linked to each other. For example, at least two of the carbons may be linked via a suitable element or group. Thus, the hydrocarbyl group may contain hetero atoms. Suitable hetero atoms will be apparent to those skilled in the art and include, for instance, sulphur, nitrogen and oxygen.
In one preferred embodiment of the present invention, the hydrocarbyl group is a hydrocarbon group.
Here the term “hydrocarbon” means any one of an alkyl group, an alkenyl group, an alkynyl group, an acyl group. The alkyl group, an alkenyl group, an alkynyl group, an acyl group groups may be linear, branched or cyclic, or an aryl group. The term hydrocarbon also includes those groups but wherein they have been optionally substituted. If the hydrocarbon is a branched structure having substituent(s) thereon, then the substitution may be on either the hydrocarbon backbone or on the branch; alternatively the substitutions may be on the hydrocarbon backbone and on the branch.
Preferably, the hydroxyhydrocarbyl group is a hydroxyalkyl group.
Preferably, the degree of substitution of the hydroxyhydrocarbyl group in the polysaccharide is from about 0.05 to about 0.9; preferably from about 0.09 to about 0.8; preferably from about 0.1 to about 0.7; preferably from about 0.2 to about 0.6.
Hydroxyalkyl Derivatives
Hydroxyalkyl derivatives of polysaccharides are derivatives where a —OH group of the polysaccharide has been replaced with a —O—R2—OH group, wherein —R2—OH is a hydroxyalkyl group.
Where a hydroxyalkyl group is present, preferably the hydroxyalkyl group has from 1 to 10 carbon atoms. The hydroxyalkyl group may be linear or branched. Preferably the hydroxyalkyl group is selected from hydroxymethyl, hydroxyethyl, hydroxypropyl and hydroxybutyl groups. More preferably the hydroxyalkyl group is a hydroxyethyl group.
Preferably the degree of substitution of the hydroxyalkyl group in the polysaccharide is from about 0.05 to about 0.9; preferably from about 0.09 to about 0.8; preferably from about 0.1 to about 0.7; preferably from about 0.2 to about 0.6.
Degree of Oxidation
Preferably, the degree of oxidation of the oxidised polysaccharide is from 1 to 100%; more preferably from 10 to 100%.
In some aspects, preferably the degree of oxidation of the oxidised polysaccharide is at least about 20%; at least about 25%; at least about 30%; at least about 40%; at least about 50%; at least about 60%; at least about 70%; at least about 75%; at least about 80%; at least about 90%.
In one aspect, preferably the degree of oxidised polysaccharide is 50% or 100%.
Weight Average Molecular Weight of the Polysaccharide
Preferably, the weight average molecular weight of the polysaccharide is from about 1 to about 2000 kDa. Preferably the weight average molecular weight of the polysaccharide is from about 8 to about 2000 kDa; preferably from about 10 to about 1000 kDa; preferably from about 25 to about 750 kDa; preferably from about 50 to about 500 kDa; preferably from about 100 to about 400 kDa; preferably from about 125 to about 250 kDa.
In one aspect the weight average molecular weight of the polysaccharide is about 1, about 10, about 25, about 70, about 125.8, about 130, about 200, about 250 or about 450 kDa,
Preferably the weight average molecular weight of the polysaccharide is about 200 kDa.
The weight average molecular weight (WAMW) of the polysaccharide can be selected to control molecular weight of the composition, circulatory half-life and biodistribution, as well as stability and protein load. Polydispersity of the polysaccharide molecular weight can also be selected with similar effect on protein properties.
Oxidised Polysaccharide
Preferably the oxidised polysaccharide contains essentially no alpha-hydroxy aldehyde units.
This proviso that the oxidised polysaccharide contains essentially no alpha-hydroxy aldehyde units means that preferably less than about 20% of the total oxidised polysaccharide monomer units contain alpha-hydroxy aldehyde units. Preferably less than about 15% of the total oxidised polysaccharide monomer units contain alpha-hydroxy aldehyde units; preferably less than about 10%; preferably less than about 5%; preferably less than about 3%; preferably less than about 2%; preferably less than about 1%.
The amount of alpha-hydroxy aldehyde units may be calculated from a consideration of the particular polysaccharide being used. For example, hydroxyethyl starch (HES) is made from natural corn starch amylopectin and consists of D-glucose monomers linked via linear α1,4 linkages. Typically in HES, approximately half of the glucose monomers are hydroxyethylated at one or more of their hydroxyl groups. Higher or lower hydroxyethylation ratios may be used to prepare HES. The α1,4 linked glucose monomers (linked to neighboring glucose monomers at both the C1 and C4 hydroxyl groups, and also at C6 if at a branch point) contain vicinal diol groups (at C2 and C3), but no 1,2,3-triol groups. Oxidation of the vicinal diols does not produce alpha-hydroxy aldehydes, which are required for the Amadori rearrangement to occur upon reaction with protein. The branch end points do contain 1,2,3-triol groups (at C2, C3 and C4) and can form alpha-hydroxy aldehyde groups upon oxidation, which would undergo the Amadori rearrangement if they react with protein. Likewise, the first monomer in the polymer also contains a 1,2,3-triol group (at C1, C2 and C3).
A method of measuring the degree of hydroxyalkylation may be found from Sommermeyer, K., Cech, F., Schmidt, M., Weidler, B.: “Hydroxyethyl starch in clinical use: A physical-chemical characterization” (German Original), Krankenhauspharmazie 8: 271 (1987).
The branching frequency in HES is 1 in every 17-20 monomers. Hence, ˜5-6% of all glucose monomers in the starch would be end points. Not all of these would be oxidizable, however, because of the hydroxyethylation in HES. Hydroxyethylation of any of the C2, C3 or C4 hydroxyl groups (members of the 1,2,3 triol) of an end monomer will prevent oxidation to an alpha-hydroxy aldehyde. Since only ˜5-6% of glucose monomers are end groups, and half of these are hydroxyethylated, and because modification of the C2 hydroxyl group accounts for at least two-thirds of hydroxylethylation in HES, then ˜3% of HES monomers could be oxidized to form alpha-hydroxy aldehydes. In other word, in a typical HES compound only ˜3% of HES monomers could form irreversible linkages with proteins.
Alpha-hydroxy aldehyde units may be formed by the partial oxidation of 1,2,3-triols.
Preferably the oxidised polysaccharide has two or more sites for conjugation with the protein. Thus, preferably the oxidised polysaccharide allows multidentate attachment to the protein.
Ratio of Oxidised Polysaccharide to Protein
Preferably the ratio of oxidised polysaccharide to protein is from 0.01:1 to 100:1; preferably the ratio is from 0.1:1 to 20:1; preferably the ratio is from 0.2:1 to 17.5:1; preferably from 0.3:1 to 16:1; preferably from 0.4:1 to 15:1; preferably from 0.5:1 to 12:1; preferably from 0.6:1 to 10:1; preferably from 0.7:1 to 9:1; preferably from 0.8:1 to 8:1.
Depending on the oxidised polysaccharide to protein ratio selected, the protein can be substantially modified with the polysaccharide to limit recognition or activity of the protein, or the protein can be polymerized through conjugation to the polysaccharide, or the protein can be presented on the outside of the oxidised polysaccharide such that recognition required for bioactivity is not impaired.
Protein
The protein component of the composition can be selected from proteins, peptides and derivatives of components thereof containing amino groups capable of reacting with aldehyde groups to form imine bonds, including proteins meeting this criteria that are described in Learner et al., Nature Reviews 2008; 7: 21-39. Proteins suitable for modification include those from various mechanistic classes (e.g., proteins replacing missing or deficient proteins, augmenting or interfering with existing pathways, providing novel function or activity, vaccines or diagnostics), functional classes (e.g., signaling, regulatory, structural, enzymatic, antibodies), structural classes (monomeric, polymeric [covalently vs. non-covalently associated], glycosylated), therapeutic classes (e.g., hormone deficiency, hemostasis and thrombosis, metabolic enzyme deficiency, pulmonary and gastrointestinal disorder, immunodeficiency, hematopoiesis, fertility, immunoregulation, endocrine disorders, growth regulation, cancer, transplantation, infectious disease, detoxification) and those proteins that have been modified using PEG (e.g., interferons, G-CSF, GM-CSF, adenosine deaminase, asparaginase, growth hormones, certolizumab, hematide, uricase), fusion proteins (e.g., interferon, tissue inhibitor metalloproteinase, interleukin, hormones), or in encapsulated forms.
Preferably, the or each protein is selected from an antibody, a cytokine, an enzyme, a peptide, a growth factor and a regulatory protein. Preferably the protein is selected from a cytokine and an enzyme.
Preferably, the or each protein is an antibody or an active fragment or homologue thereof. Preferably the antibody is selected from anti-tumour necrosis factor alpha antibody (Anti-TNFα), CD163 antibody, anti-VEGF, anti-thrombin antibody, anti-CD20 antibody, anti-IgG1 antibody, anti-HER2 antibody, anti-CD33 antibody, anti-IgG2a antibody and anti-EGFR antibody.
Preferably, the or each protein is a cytokine. Preferably the cytokine is selected from interferon (IFN), erythropoietin (EPO) and granulocyte-colony stimulating factor (G-CSF).
Preferably, the or each protein is an enzyme. Preferably the enzyme is selected from uricase, elastase, streptokinase, asparaginase and beta-glucocerebrosidase.
Preferably, the or each protein is a growth factor. Preferably the growth factor is insulin.
Preferably, the or each protein is a regulatory protein. Preferably the regulatory protein is selected from C1 esterase inhibitor and alpha-1 antitrypsin.
For some proteins the activity is dependent on interaction of a protein site with substrates, co-factors, inhibitors, activators, receptors, ligands, allosteric modulators or other interacting molecules. The protein site for such interaction may be obstructed by steric hindrance or direct modification by the polysaccharide in the conjugate, or by other protein molecules in a composition or formulation comprising the conjugate, to result in decreased activity of the protein. Upon release of the protein from the conjugated form, steric hindrance is removed, such that activity increases relative to the conjugated form of the protein. This property of the composition may be especially pronounced in cases where the interacting molecule is not small enough to access, or is blocked from, the protein's reactive site when the site is hindered in such a way to prevent access.
In the case where the protein activity is dependent on intramolecular movement (at the secondary, tertiary or quaternary level), or is dependent on interaction between subunits of the protein, this movement or interaction may be obstructed by steric hindrance or direct modification by the polysaccharide in the conjugate, or by other protein molecules in a composition or formulation comprising the conjugate, to result in decreased activity of the protein. Upon release of the protein from the conjugated form, steric hindrance is removed, such that activity increases relative to the conjugated form of the protein.
Multiple copies of the protein of interest may be incorporated into the conjugate, which may improve recognition events in which multiple local stimuli by the protein are required or are beneficial, such as with certain cell surface receptors.
Proteins and peptides universally contain amino groups that may be used to attach the protein to an oxidised polysaccharide without the need for activating agents or additional chemical linkers.
The protein may comprise more than one amino group and may be conjugated to the oxidised polysaccharide by one or more imine bonds. The protein may be conjugated to the oxidised polysaccharide by two or more imine bonds.
Preferably, the oxidised polysaccharide-protein conjugate comprises a protein whose solubility is increased in the conjugate as compared to the non-conjugated protein.
Preferably, the or each protein is selected from EPO, G-CSF, uricase, beta-glucocerebrosidase, alpha-galactosidase, C-1 inhibitor, streptokinase, DNAseI, alpha-1 antitrypsin, asparaginase, arginine deiminase, Factor IX, Factor VIIa, Factor VIII, Factor IIa (thrombin), anti-TNF-alpha antibody, tissue plasminogen activator, human growth hormone, superoxide dismutase, catalase, CD163 antibody, anti-VEGF, anti-thrombin antibody, anti-CD20 antibody, anti-IgG1 antibody, anti-HER2 antibody, anti-CD33 antibody, anti-IgG2a antibody, anti-EGFR antibody, histone, interferon, insulin, albumin and mixtures thereof.
Preferably, the or each protein has a weight average molecular weight of greater than about 1 kDa; preferably greater than 8 kDa; preferably greater than 10 kDa; preferably greater than 20 kDa; preferably greater than 30 kDa; preferably greater than 40 kDa; preferably greater than 50 kDa.
Preferably, the or each protein has a weight average molecular weight of from 8 kDa to 1000 kDa; preferably from 20 kDa to 900 kDa; preferably from 50 to 800 kDa.
Preferably, the histone is histone H1.
In one aspect, the or each protein is a labeled protein. Suitably, the protein is labeled with a fluorescent label.
Concentration of Protein
Preferably the reaction concentration of protein in step (b) is from about 0.01 to about 10 g/L; preferably from about 0.1 to about 5 g/L; preferably from about 0.2 to about 4 g/L; preferably from about 0.3 to about 2 g/L; preferably from about 0.5 to about 1.5 g/L; preferably from about 0.8 to about 1.2 g/L.
Method
Preferably, the method comprises the step:                (a) selecting a polysaccharide that contains essentially no 1, -2, -3-triol monomer units and oxidising said polysaccharide with an oxidising agent to form an oxidised polysaccharide; and        (b) reacting the oxidised polysaccharide with a protein to form a composition comprising a conjugate wherein the oxidised polysaccharide and the protein are conjugated via one or more imine bonds.        
Optionally, the oxidised polysaccharide may be purified to remove the oxidizing agent and its by-products. This purification may comprise the step of diafiltration using a molecular weight cut-off membrane. Suitable membranes include 1 kDa, 5 kDa, 10 kDa, 50 kDa and 100 kDa molecular weight cut-off membrane.
Preferably, the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a molecular crowding agent.
Preferably, the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a reducing agent.
Preferably, the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a molecular crowding agent and in the absence of a reducing agent.
Optionally, the composition formed in step (b) may be purified to remove ions and polysaccharide-based components below a selected molecular weight. This purification may comprise the step of dialyzing a solution containing the conjugate against a solvent using a dialysis membrane or by diafiltration. Suitably the solvent is phosphate-buffered saline or another physiologically acceptable buffer. Suitably the dialysis membrane is selected with a 2, 3.5, 7, 10, 20, 50 or 100 kDa molecular weight cut-off. Suitably the dialysis membrane has a 10 kDa molecular weight cut-off.
In one aspect, the oxidised polysaccharide is reacted with a protein in step (b) in the presence of at least one further protein such that the oxidised polysaccharide-protein composition comprises more than one protein and each protein is conjugated to the oxidised polysaccharide via one or more imine bonds. In this aspect, preferably there is one further protein. Suitably, the protein is streptokinase and the further protein is albumin.
Optionally, the composition may be purified by chromatography.
Optionally, the composition may be a purified molecular weight fraction following the removal of low and/or high molecular weight components.
Optionally, the method may comprise a further step (c) of freeze-drying the composition, or formulating the composition at a concentration, pH and ionic strength that stabilizes the composition.
Oxidising Agent
Preferably the oxidising agent is a periodate compound. Preferably the periodate compound is an alkali metal periodate compound. Suitable oxidizing agents are selected from lithium periodate, sodium periodate and potassium periodate.
Preferably the oxidising agent is sodium periodate.
pH
Preferably step (b) is carried out at a pH of from 6 to 10 at room temperature (26° C.); preferably a pH of from 6.5 to 9; preferably a pH of from 7 to 8.
In some aspects, the pH of the oxidised polysaccharide-protein composition is lowered to a pH of from 5 to 6 (as measured at room temperature 25° C.) for formulations purposes.
Reaction Time
Preferably the oxidised polysaccharide is reacted with a protein in step (b) for from 0.01 to 100 hours; preferably from 0.01 to 80 hours; preferably from 0.01 to 72 hours; preferably from 0.01 to 48 hours; preferably from 0.01 to 36 hours; preferably from 0.02 to 24 hours.
Temperature
Preferably step (a) is carried out at a temperature of less than 20° C.; preferably less than 15° C.; preferably less than 10° C.; preferably less than 5° C.
Preferably step (b) is carried out at temperature of at least 5° C.; preferably at least 10° C.; preferably at least 15° C.; preferably at least 20° C.
In one aspect, preferably step (b) is carried out at temperature of from 5 to 50° C.; preferably from 10 to 48° C.; preferably from 15 to 45° C.; preferably from 20 to 42° C.; preferably from 25 to 40° C.
Treatment or Diagnosis of a Disease or Condition
As discussed herein, the conjugate or compositions containing the conjugate may be used for the treatment or diagnosis of a range of disorders. The disorder may be selected from oncology, infectious disease, metabolic disorders, cardiovascular disorders.
As discussed herein, the conjugate or compositions containing the conjugate may be used for the treatment or diagnosis of a disease or condition. The disease or condition may suitably be selected from hormone deficiency, hemostasis, thrombosis, metabolic enzyme deficiency, pulmonary disorder, gastrointestinal disorder, immunodeficiency, hematopoiesis, fertility disorders, immunoregulation, endocrine disorders, hemophilia, shock, growth regulation, cancer, transplantation, infectious disease, inflammation and detoxification.
Preferably the disorders/diseases or condition may suitably be selected from hepatitis C virus (HCV) infection, acute lymphoblastic leukemia (ALL), chronic obstructive pulmonary disorder (COPD), alpha-1 antitrypsin (AAT) deficiency, anemia, chronic hyperuricemia, hemophilia, hemorrhage, chemotherapy-induced neutropenia, Gaucher's disease, Fabry's disease, hereditary angioedema, malignant melanoma, hepatocellular carcinoma (HCC), reperfusion injury, myocardial infarction, pulmonary embolism, psoriasis, Crohn's disease, rheumatoid arthritis, ulcerative colitis, cystic fibrosis, hemophilia A, hemophilia B, von Willebrand disease, diabetes, sepsis, hypovolemic shock and growth hormone deficiency.
Preferably the composition is administered to a subject and the protein is released from the conjugate over time such that the circulatory half-life of the protein that is conjugated is enhanced relative to the circulatory half-life of non-conjugated protein
Other Features
Preferably, the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a molecular crowding agent. Preferably, the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a macromolecular crowding agent. For the purposes of this specification a macromolecular crowding agent is defined herein as a compound that attracts water and allows molecules to aggregate. Examples of macromolecular crowding agents are soluble, linear polymers such as polyvinylpyrrolidone, polyehthylene glycol, dextran, nonylphenol-thoxylates, polyvinyl alcohol and mixtures thereof.
Optionally, the composition or conjugate may be freeze-dried, or formulated at a concentration, pH and ionic strength that stabilizes the composition or conjugate.
Size and in vivo stability of a protein-polysaccharide composition can be controlled through proper selection of degree of hydroxyethylation or other modification of the polysaccharide (e.g., oxidation), which will control the rate of dissociation or degradation of the polysaccharide and release of the protein. Additionally, size and in vivo stability of a protein-polysaccharide composition can be controlled through proper selection of pH of conjugation, protein concentration during conjugation, temperature during conjugation, duration of conjugation, excipients added after conjugation and formulation of the conjugate.
In a further aspect, there is provided an oxidised polysaccharide-protein composition or conjugate as described herein wherein the degree of oxidation of the oxidised polysaccharide, and/or the weight average molecular weight of the polysaccharide, and/or ratio of oxidised polysaccharide to protein, and/or degree of substitution of the hydroxyhydrocarbyl group in the polysaccharide, and/or the polydispersity of the polysaccharide is used to control:                activity of the protein in the composition;        activity of the conjugated protein;        activity of the released protein;        circulatory half-life of the protein;        rate of release of active protein from the conjugate;        stability of the conjugate vs degradation;        solubility of the conjugated protein        
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate or a composition as described herein wherein the conjugate is capable of releasing protein in presence of plasma components.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate or a composition as described herein wherein the linkage between the protein and the oxidized polysaccharide is dissociated by processes such as non-enzymatic hydrolysis and transimination under physiological conditions.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate, a composition or processes as described herein for selected conjugate stability in plasma.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate, a composition or processes as described herein for selected conjugate stability in solution, with majority of protein maintained in the conjugated form or maintenance of a selected non-conjugated:conjugated protein ratio, optionally controlled by selection of pH, ionic strength or concentration of the composition.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate or a composition as described herein wherein the protein is an enzyme and the conjugate or composition has a masked, latent, dormant or preserved enzyme activity.
In a further aspect, there is provided an oxidised polysaccharide-protein conjugate, a composition or processes as described herein for increasing in vivo half-life or bioactivity of the protein.
In a further aspect, there is provided a method of reversibly conjugating a protein to an oxidised polysaccharide comprising the steps of preparing an oxidised polysaccharide-protein composition as described herein, and dissolving the oxidised polysaccharide-protein composition in a solvent.
Specific Combinations
Suitably the conjugates, compositions, methods and uses as described herein may comprise a polysaccharide selected from starch and hydroxyethyl starch, and a protein that is interferon. Suitably the degree of oxidiation of the oxidised polysaccharide is selected from 1, 10, 25, 50, 75 and 100% to increase the half-life of interferon. Suitably hydroxyethyl starch with a weight average molecular weight from about 1, 10, 25, 70, 200, or 450 kDa is used to increase the half-life of interferon and/or allow gradual release of the active interferon in circulation. Suitably starch with a weight average molecular weight of about 125.8 kDa is used to increase the half-life of interferon and/or allow gradual release of the active interferon in circulation. Suitably the composition has increased activity half-life/duration of activity compared to interferon.
The amino groups of interferon may be conjugated to the oxidised starch or hydroxyethyl starch by more than one imine bond.
Suitably the conjugates, compositions, methods and uses as described herein may comprise a 200 kDa hydroxyethyl starch-protein formulation wherein the protein is an enzyme which has reduced activity in the conjugated form, compared to the enzyme released from the conjugate. Suitably the enzyme is selected from uricase, elastase, asparaginase, streptokinase and beta-glucocerebrosidase.
Suitably the conjugates, compositions, methods and uses as described herein may comprise a 200 kDa hydroxyethyl starch-protein formulation wherein the protein is a regulatory protein. Suitably the regulatory protein is selected from C1 esterase inhibitor and alpha-1 antitrypsin.
Suitably the conjugates, compositions, methods and uses as described herein may comprise a 200 kDa hydroxyethyl starch-protein formulation wherein the protein is a cytokine. Suitably the cytokine is selected from interferon (IFN), erythropoietin (EPO) and granulocyte-colony stimulating factor (G-CSF).
Suitably the conjugates, compositions, methods and uses as described herein may comprise a 200 kDa hydroxyethyl starch-protein formulation wherein the protein is an antibody. Suitably the antibody is selected from anti-tumour necrosis factor alpha antibody (Anti-TNFα), anti-thrombin and anti-CD163. Other examples include Rituxan® (anti-CD20) Idec-Genentech, Mylotarg® (anti-CD33) Wyeth, Avastin® (anti-VEGF), anti-IgG1 (Herceptin®) Genentech, anti-HER2 (Herceptin®) Genentech, anti-IgG2a (Bexxar®) Corixam-GSK and anti-EGFR (Erbitux®) Imclone.
Hydroxyethyl Starch
A preferred polysaccharide is hydroxyethyl starch. Hydroxyethyl starch has been widely used as an approved blood volume expander for decades and has been infused in large volumes (˜3 g hydroxyethyl starch/kg body weight) into a large number of and wide range of patients.
Hydroxyethyl starch is an approved modified form of naturally occurring starch and may therefore be more biologically compatible (e.g., readily metabolized) than other macromolecules, especially those that are synthetic.
The hydroxyethyl starch-protein link involves the direct interaction of aldehydes on the oxidised hydroxyethyl starch with amino groups on the protein to form an imine bond, with no intervening chemical linker.
Large conjugates with correspondingly increased half-life and protein load are possible for hydroxyethyl starch modification, owing to the high molecular weights of hydroxyethyl starch available, and because of the possibility of oligomerization. The hydroxyethylation of starch increases the stability of the starch by impairing amylase degradation in vivo.
Suitably conjugates of oxidized hydroxyethyl starch and protein may have                up to 100% of vicinal dials in the hydroxyethyl starch have been oxidized to aldehydes, or        the protein contains amino groups capable of forming imine linkages with the aldehydes of the oxidized hydroxyethyl starch, or        the majority of protein is conjugated to the oxidized hydroxyethyl starch through imine linkages, or        activity of the conjugated protein may be decreased relative to non-conjugated protein, or        the majority of the conjugated protein is capable of being released from the conjugate, or        activity of the released protein is greater than or equal to the conjugated protein, or        activity of the released protein is less than the conjugated protein (in the possible case where HES bulk aids in receptor recognition or binding of substrates, etc.).        
Further aspects of the invention are provided in the following numbered paragraphs.
(1) A method of preparing an oxidised polysaccharide-protein composition comprising the steps of:                (a) oxidising a polysaccharide with an oxidising agent to form an oxidised polysaccharide; and        (b) reacting the oxidised polysaccharide with a protein to form a composition comprising a conjugate wherein the oxidised polysaccharide and the protein are conjugated via one or more imine bonds; and        (c) optionally lowering the pH of the oxidised polysaccharide-protein conjugate to a pH of from 5 to 6 for formulation purposes.        
(2) A method according to paragraph (1), wherein with the polysaccharide is a polysaccharide that contains essentially no 1,2,3-trial monomer units.
(3) A method according to paragraph (2) wherein the 1,2,3-triol monomer units are partially or completely alkylated to prevent formation of alpha-hydroxy aldehyde groups upon oxidation of the triol.
(4) A method according to any one of the preceding numbered paragraphs, wherein the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a molecular crowding agent.
(5) A method according to any one of the preceding numbered paragraphs, wherein the oxidised polysaccharide is reacted with a protein in step (b) in the absence of a reducing agent.
(6) A method according to any one of the preceding numbered paragraphs, wherein the polysaccharide is selected from cellulose, pectin, starch and hydroxyhydrocarbyl derivatives thereof.
(7) A method according to any one of the preceding numbered paragraphs, wherein the polysaccharide is selected from cellulose, pectin, starch, hydroxalkyl cellulose and hydroxalkyl starch.
(8) A method according to any one of the preceding numbered paragraphs, wherein the polysaccharide is hydroxyethyl starch.
(9) A method according to any one of the preceding numbered paragraphs, wherein the degree of oxidation of the oxidised polysaccharide is from 1 to 100%.
(10) A method according to any one of the preceding numbered paragraphs, wherein the weight average molecular weight of the polysaccharide is from 1 to 2000 kDa.
(11) A method according to any one of the preceding numbered paragraphs, wherein the ratio of oxidised polysaccharide to protein is from 0.1:1 to 20:1.
(12) A method according to any one of the preceding numbered paragraphs, wherein step (a) is carried out at temperature of less than 10° C.
(13) A method according to any one of the preceding numbered paragraphs, wherein step (b) is carried out at temperature of at least 10° C.
(14) A method according to any one of the preceding numbered paragraphs, wherein the oxidising agent is a periodate compound.
(15) A method according to any one of the preceding numbered paragraphs, wherein the oxidised polysaccharide is reacted with a protein in step (b) in the presence of at least one further protein such that the oxidised polysaccharide-protein composition comprises more that one protein and each protein is conjugated to the oxidised polysaccharide via one or more imine bonds.
(16) A method according to any one of the preceding numbered paragraphs, wherein the or each protein is selected from antibodies, cytokines, enzymes, growth factors and regulatory proteins.
(17) A method according to any one of the preceding numbered paragraphs, wherein the or each protein is selected from erythropoietin (EPO), granulocyte-colony stimulating factor (G-CSF), uricase, beta-glucocerebrosidase, alpha-galactosidase, C-1 inhibitor, streptokinase, DNAseI, alpha-1 antitrypsin, asparaginase, arginine deiminase, Factor IX, Factor VIIa, Factor VIII, Factor IIa (thrombin), anti-TNF-alpha antibody, tissue plasminogen activator, human growth hormone, superoxide dismutase, catalase, CD163 antibody, anti-VEGF, anti-thrombin antibody, anti-CD20 antibody, anti-IgG1 antibody, anti-HER2 antibody, anti-CD33 antibody, anti-IgG2a antibody, anti-EGFR antibody, histone, interferon, insulin, albumin and mixtures thereof.
(18) A method according to any one of the preceding numbered paragraphs wherein the oxidized polysaccharide contains essentially no alpha hydroxyl aldehyde units.
(19) A method according to any one of the preceding numbered paragraphs wherein the oxidised polysaccharide-protein conjugate is less than 0.1 μm in size.
(20) A method according to any one of the preceding numbered paragraphs wherein the oxidised polysaccharide has two or more sites for conjugation with the protein.
(21) A method according to any one of the preceding numbered paragraphs wherein the protein has a weight average molecular weight of greater than about 1 kDa.
(22) A method according to any one of the preceding numbered paragraphs, wherein the oxidised polysaccharide-protein composition further comprises non-conjugated protein.
(23) An oxidised polysaccharide-protein composition obtained by the method of any one of the preceding numbered paragraphs.
(24) An oxidised polysaccharide-protein composition comprising an oxidised polysaccharide and a protein; wherein the oxidised polysaccharide comprises essentially no alpha-hydroxy aldehyde units and wherein the protein is conjugated to the oxidised polysaccharide via one or more imine bonds.
(25) An oxidised polysaccharide-protein composition according to paragraph (22) comprising the features as described in any one of paragraphs (1) to (22).
(26) An oxidised polysaccharide-protein composition for use in the treatment or diagnosis of a disease or condition wherein the protein is conjugated to the oxidised polysaccharide via one or more imine bonds.
(27) An oxidised polysaccharide-protein composition according to paragraph (26) wherein the oxidised polysaccharide contains essentially no alpha-hydroxy aldehyde units.
(28) An oxidised polysaccharide-protein composition according to paragraph (26) or (27), wherein the composition was obtained or obtainable by the method of any one of paragraphs (1) to (22).
(29) An oxidised polysaccharide-protein composition according to any one of paragraphs (26) to (28), wherein the disease or condition is selected from hormone deficiency, hemostasis, thrombosis, metabolic enzyme deficiency, pulmonary disorder, gastrointestinal disorder, immunodeficiency, hematopoiesis, fertility disorders, immunoregulation, endocrine disorders, hemophilia, shock, growth regulation, cancer, transplantation, infectious disease, inflammation and detoxification.
(30) An oxidised polysaccharide-protein composition according to any one of paragraphs (26) to (29), wherein the disease or condition is selected from hepatitis C virus (HCV) infection, acute lymphoblastic leukemia (ALL), chronic obstructive pulmonary disorder (COPD), alpha-1 antitrypsin (AAT) deficiency, anemia, chronic hyperuricemia, hemophilia, hemorrhage, chemotherapy-induced neutropenia, Gaucher's disease, Fabry's disease, hereditary angioedema, malignant melanoma, hepatocellular carcinoma (HCC), reperfusion injury, myocardial infarction, pulmonary embolism, psoriasis, Crohn's disease, rheumatoid arthritis, ulcerative colitis, cystic fibrosis, hemophilia A, hemophilia B, von Willebrand disease, diabetes, sepsis, hypovolemic shock and growth hormone deficiency.
(31) An oxidised polysaccharide-protein composition any one of paragraphs (26) to (30), wherein the composition is administered to a subject and the protein is released from the conjugate over time such that the circulatory half-life of the protein that is conjugated is enhanced relative to the circulatory half-life of non-conjugated protein.
(32) A method of reversibly conjugating a protein to an oxidised polysaccharide comprising the steps of preparing an oxidised polysaccharide-protein composition according to any one of paragraphs (1) to (22), and dissolving the oxidised polysaccharide-protein composition in a solvent.
(33) Use of an oxidised polysaccharide-protein composition according to any one of paragraphs (23) to (25), to solubilise the protein.
(36) Use according to paragraph (33), wherein the protein is insulin,